Conventionally, a laser head device of a three-dimentional processing type is used in laser cutting of a three-dimentional figure (solid) workpiece by a laser processing apparatus. The laser head device is comprised of a Z-axis moving body movable upwardly and downwardly (in a Z-axis direction), a A-axis rotary body rotatable about an axis of the Z-axis moving body (in a A-axis direction), and a B-axis rotary body rotatable about an axis perpendicular to the A-axis rotary body (in a B-axis direction) and carrying at its lower end a nozzle.
In a mechanism for driving the Z-axis moving body, the output of a Z-axis motor is reduced in speed by a pair of bevel gears and transmitted to a pinion wherein rotation of the pinion is converted into vertical linear motion of a rack. The rack is fixed to the Z-axis moving body, and therefore the Z-axis moving body moves in the Z-axis direction while being guided by a linear motion guide.
Also, in a mechanism for driving the B-axis rotary body, the output of a B-axis motor which is secured to the A-axis rotary body, is transmitted to a spur gear attached to the B-axis rotary body, and therefore the B-axis rotary body rotates in the B-axis direction.
By the way, in order to drive or move the Z-axis moving body of the above-mentioned conventional laser head device in the Z-axis direction, the driving power is transmitted through three pairs of gears the pairs of which require an intricate backlash cancelling mechanism which is difficult to be assembled and maintained. Furthermore, the Z-axis moving body needs a balancer such as a spring because of heavy weight of the Z-axis moving body.
For cancelling a backlash of a spur gear and a pinion to rotate the A-axis rotary body, the spur gear is divided into two pieces in the direction of its thickness, and phases of the two pieces are slightly shifted, thereby a tooth of the pinion is pinched therebetween. Furthermore, the A-axis rotary body is therein provided with a pipe body through which laser beams pass. Thus, the structure of the device is complicated, which makes assembling of it difficult.
In addition, a backlash cancelling mechanism is required to rotate the B-axis rotary body as required for the A-axis rotary body, and the B-axis rotary body may seriously be in contact with a workpiece. Furthermore, due to its structure, the spur gear cannot be provided with dust-proof means and as a result gathers rust or spatters produced during laser processing. The spur gear also requires slip rings for relaying a cable of the B-axis motor, which will cause a rise in cost.
The object of the present invention is to improve the above-mentioned problems and to provide a laser head device which is simple, compact, and lightweight as a whole in structure wherein a A-axis rotary body serves both as a protecting means for protecting and allowing laser beams to pass therethrough and a rotary shaft.